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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment.
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
An initial loading rate of 200 mg/L was stirred fir a period of at least 24 hours in a closed test bottle. Subsequently, synthetic sewage feed and sludge were added resulting in a final loading of 100 mg/L.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Sludge originated from the municipal sewage treatment plant "Waterschap de Maaskant in Den Bosch, the Netherlands".

Upon retrieval the sludge was coarsely sieved and diluted with ISO-medium. The amount of suspended solids was 3.9 g/L.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
18.1 to 18.9 ºC
pH:
8.6
Nominal and measured concentrations:
Nominal: 100 mg/L
Details on test conditions:
TEST SYSTEM
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: glass, 1 L
- Aeration: yes
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Effect concentrations exceeding solubility of substance in test medium: yes
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 20.1 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The 3-h EC50 value of AC-6000 in domestic activated sludge is >100 mg/L.
Executive summary:

In a GLP-compliant OECD 209 guideline study for AC-6000with predominantly domestic sludge, activated sludge (0.7 g/L suspended solids, 2 replicates) was exposed to a nominal concentration of 100 mg/L for 3 hours.




The test concentration was prepared by stirring the test solution with a target dose level of 200 mg/L for 24 hours before exposure. The growth inhibition rate of the test substance was 9%. The 3-h EC50 value is >100 mg/L, this effect concentration is larger than the water solubility.

Description of key information

The 3-h EC50 value of AC-6000 in domestic activated sludge is >100 mg/L; this value will be used in the assessment.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

A GLP-compliant OECD 209 guideline study with predominantly domestic sludge is available for AC-6000 (NOTOX B.V., 2007). Activated sludge (0.7 g/L suspended solids, 2 replicates) was exposed to a nominal concentration of 100 mg/L for 3 hours.

The test concentration was prepared by stirring the test solution with a target dose level of 200 mg/L for 24 hours before exposure. The growth inhibition rate of the test substance was 9%. The 3-h EC50 value is >100 mg/L, this effect concentration is larger than the water solubility.

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